The present invention relates to the problem of non-obtrusively and rapidly identifying signs of emotional stress in an individual, and in particular to rapidly and non-obtrusively screening individuals for probability of attempted deception and malevolent intent.
For example, to reduce the risk of terrorism or other malfeasance by providing a tool to help in the security-screening of airline passengers, such tool giving a rapid indication of suspicion that a given passenger may be attempting to deceive a security screening officer. The invention would also be useful at border-crossings and other sensitive, high-traffic locations.
Security screening of airline passengers has become a critical priority since Sep. 11 2001. However, the techniques that are currently available to accomplish this are problematic:                Screening for weapons is insufficiently reliable, as demonstrated by the ease with which the September 11 terrorists and the later “Shoe-Bomber” were able to board aircraft with lethal materials.        Human interpreted questioning of passengers by airline security personnel has low probability of uncovering trained terrorists.        More sophisticated interrogation and “profiling” of passengers is controversial, disruptive to the boarding process, and depends on highly skilled and trained security personnel.        
In theory, polygraphic (“liedetection”) technologies could be extremely useful for improving airline passenger screening. Polygraphs sense minute changes in physiological signals to indicate a person's level of anxiety as he or she answers questions. A trained polygraphist can use these anxiety measures to identify suspicious answers.
Polygraphic techniques are well known. They are based on detecting and analyzing known physiological correlates of enhanced stress while questioning a subject Common physiological correlates used in conventional polygraphic techniques are changes in respiration, heart-rate, and electrodermal activity (sweat gland activity).
However, conventional polygraphic technologies are not suited to mass-screening applications such as those required for passenger screening at airports. This is because conventional polygraphy techniques are complicated and time-consuming to administer, requiring multiple sensors to be carefully attached to the subject's body. Administering a standard polygraph test to pre-boarding passengers might take several days per airplane.
The following description from the American Polygraph Association, highlights the complex and time consuming nature of standard polygraphy techniques:    It is important to understand what a polygraph examination entails. A polygraph instrument will collect physiological data from at least three systems in the human body. Convoluted rubber tubes that are placed over the examinee's chest and abdominal area will record respiratory activity. Two small metal plates, attached to the fingers, will record sweat gland activity, and a blood pressure cuff, or similar device will record cardiovascular activity.    A typical polygraph examination will include a period referred to as a pre-test, a chart collection phase and a test data analysis phase. In the pre-test, the polygraph examiner will complete required paperwork and talk with the examinee about the test. During this period, the examiner will discuss the questions to be asked and familiarise the examinee with the testing procedure. During the chart collection phase, the examiner will administer and collect a number of polygraph charts. Following this, the examiner will analyze the charts and render an opinion as to the truthfulness of the person taking the test. The examiner, when appropriate, will offer the examinee an opportunity to explain physiological responses in relation to one or more questions asked during the test.—The American Polygraph Association website, Jun. 17, 2002.
In addition to the above procedure, the polygraphic examiner will typically visually observe the subject looking for gross activities (such as fidgeting) that are known to be consistant with stress and therefore elevate suspicion of deception. “Activity sensors” are sometimes used in conjunction with conventional polygraph equipment to assist the examiner in observing such gross activities.
For example the Model 76875AS. Available from Lafayette Instrument Company, 3700 Sagamore Parkway North, Lafayette, Ind. 47903, USA. The following extract from the brochure of the abovementioned activity sensor provides indication of the use of the activity sensor “By providing a graphic record of subject movement, the Activity Sensor allows the polygraph examiner to concentrate on administering the exam instead of trying to observe the subject's movement”—Lafayette Instrument Company New Polygraph Catalog (Downloaded from www.lafayetteinstrument.com/ on Jun. 17, 2002).
In summary therefore, conventional polygraphic technologies are not useful for rapidly and unobtrusively assessing probable deception or emotional arousal in general.
There has been research dedicated towards identifying physiological correlates with stress different from those mentioned above, some of which may require less intrusive wiring of subjects.
U.S. Pat. No. 5,853,005 (Scanlon) teaches building a hydrophone into a seat or chair so as to measure voice stress levels, heart and breath rate, and body temperature for surreptitious interrogation or identification. But these parameters are well studied polygraphic parameters, and are not themselves or in combination known to be sufficient for rapid deception screening.
U.S. Pat. No. 5,137,027 (Rosenfeld.)—Teaches evaluating whether a subject has performed a given act by analyzing P300 brain waves. But this approach requires obtrusive head-mounted sensors.
U.S. Pat. No. 5,507,291 (Stirbl et. al.)—Teaches remotely measuring parameters such as blood pressure, pulse rate, pupil size, respiration rate and perspiration level by transmitting a generated waveform at a remotely located subject and analyzing the result.
U.S. Pat. No. 5,771,261 (Anbar)—Teaches Telethermometric psychological evaluation by monitoring of changes in skin perfusion induced by the autonomic nervous system.
U.S. Pat. No. 5,774,571 (Marshall)—Teaches using a pen incorporating a trembling sensor to ascertain likely signs of stress and therefore deception on the part of the person writing with the pen.
U.S. Pat. No. 5,876,334 (Levi)—Teaches lie detection based on analyzing response time to specific carefully formed questions.
U.S. Pat. No. 6,388,739 (Rice)—teaches of detecting vital-signs of an individual from a distance via a self-referencing microdoppler ladar receiver.
In addition to the above prior-art, reference has been noted in the literature to efforts to assess deception and emotional stress by measuring pupil-dilation, measuring thermal differentials of areas of the face or body, visually analyzing facial expressions, analyzing ocular activities (e.g., eye blinking), and analyzing vocal tremors and other changes in voice characteristics.
However, there are no indications that any of the above less-obtrusive approaches in and of themselves can be sufficiently rapid and reliable to solve the mass screening need described above.